Deletions of both alpha 5(IV) and alpha 6(IV) collagen genes in Alport syndrome and in Alport syndrome associated with smooth muscle tumours

Clinical Manifestations of Alport Syndrome-Diffuse Leiomyomatosis Patients With Contiguous Gene Deletions in COL4A6 and COL4A5

Alport syndrome-diffuse leiomyomatosis is a rare type of X-linked Alport syndrome resulting from contiguous deletions of 5′ exons of COL4A5 and COL4A6. Studies have suggested that the occurrence of diffuse leiomyomatosis is associated with the characteristic localisation of the COL4A6 gene deletion break point. An electronic database was searched for all studies accessing AS-DL to analyze the clinical characteristics, gene deletion break points of patients with AS-DL, and the pathogenesis of AS-DL. It was found that the proportion of de novo mutations of AS-DL was significantly higher in female probands than male probands (78 vs. 44%). Female patients with AS-DL had a mild clinical presentation. The incidence of proteinuria and ocular abnormalities was much lower in female probands than in male probands, and there was generally no sensorineural hearing loss or chronic kidney disease (CKD), which progressed to Stage 3 in female probands. The contiguous deletion of the 5' exons of COL4A5 and COL4A6, with the break point within the intron 3 of COL4A6, was the critical genetic defect causing AS-DL. However, the pathogenesis of characteristic deletion of COL4A6 that contributes to diffuse leiomyomatosis is still unknown. In addition, characteristic contiguous deletion of COL4A5 and COL4A6 genes in AS-DL may be related to transposed elements (TEs).

Molecular and Cellular Insights into the Development of Uterine Fibroids

Uterine leiomyomas represent the most common benign gynecologic tumor. These hormone-dependent smooth-muscle formations occur with an estimated prevalence of ~70% among women of reproductive age and cause symptoms including pain, abnormal uterine bleeding, infertility, and recurrent abortion. Despite the prevalence and public health impact of uterine leiomyomas, available treatments remain limited. Among the potential causes of leiomyomas, early hormonal exposure during periods of development may result in developmental reprogramming via epigenetic changes that persist in adulthood, leading to disease onset or progression. Recent developments in unbiased high-throughput sequencing technology enable powerful approaches to detect driver mutations, yielding new insights into the genomic instability of leiomyomas. Current data also suggest that each leiomyoma originates from the clonal expansion of a single transformed somatic stem cell of the myometrium. In this review, we propose an integrated cellular and molecular view of the origins of leiomyomas, as well as paradigm-shifting studies that will lead to better understanding and the future development of non-surgical treatments for these highly frequent tumors.

Missense mutations in COL4A5 or COL4A6 genes may cause cerebrovascular fibromuscular dysplasia: Case report and literature review

INTRODUCTION

Fibromuscular dysplasia (FMD) is a rare and controversial disease that is seldom associated with genes. Here, we report the discovery of 2 missense mutations in COL4A5 and COL4A6 that may be risk factors for causing cerebrovascular FMD. We performed high-throughput sequencing on a patient with FMD and her probable healthy daughter, then annotated the frequency of a variant in a control or general population and assessed its deleterious effects according to published guidelines.

CONCLUSIONS

We identified missense mutations in COL4A5 (exon43:c.C3940 > T:p.P1314S) and COL4A6 (exon36:c.C3538 > T:p.P1180S) from the proband and her daughter. Sanger sequencing revealed that these probable causal variants were passed to her from her mother. The two missense mutations may have complex functional effects on the integrity of the cerebral vessel walls, including modulating collagens and promoting angiogenesis expression, may be responsible for cerebrovascular FMD.

Cell therapy for basement membrane-linked diseases

For most disorders caused by mutations in genes encoding basement membrane (BM) proteins, there are at present only limited treatment options available. Genetic BM-linked disorders can be viewed as especially suited for treatment with cell-based therapy approaches because the proteins that need to be restored are located in the extracellular space. In consequence, complete and permanent engraftment of cells does not necessarily have to occur to achieve substantial causal therapeutic effects. For these disorders cells can be used as transient vehicles for protein replacement. In addition, it is becoming evident that BM-linked genetic disorders are modified by secondary diseases mechanisms. Cell-based therapies have also the ability to target such disease modifying mechanisms. Thus, cell therapies can simultaneously provide causal treatment and symptomatic relief, and accordingly hold great potential for treatment of BM-linked disorders. However, this potential has for most applications and diseases so far not been realized. Here, we will present the state of cell therapies for BM-linked diseases. We will discuss use of both pluripotent and differentiated cells, the limitation of the approaches, their challenges, and the way forward to potential wider implementation of cell therapies in the clinics.

Chinese family with diffuse oesophageal leiomyomatosis: a new COL4A5/COL4A6 deletion and a case of gonosomal mosaicism

BACKGROUND

Diffuse oesophageal leiomyomatosis (DOL) is a rare disorder characterized by tumorous overgrowth of the muscular wall of the oesophagus. DOL is present in 5 % of Alport syndrome (AS) patients. AS is a rare hereditary disease that involves varying degrees of hearing impairment, ocular changes and progressive glomerulonephritis leading to renal failure. In DOL-AS patients, the genetic defect consists of a deletion involving the COL4A5 and COL4A6 genes on the X chromosome.

CASE PRESENTATION

We report a two-generation family (4 individuals; parents and two children, one male and one female) with two members (mother and son) affected with oesophageal leiomyomatosis. Signs of potential renal failure, which characterizes AS, were only apparent in the index patient (son) 2 years and three months after the initial diagnosis of DOL. Blood DNA from the four family members were submitted to exome sequencing and array genotyping to perform a genome wide screening for disease causal single nucleotide (SN) and copy number (CN) variations. Analyses revealed a new 40kb deletion encompassing from intron 2 of COL4A5 to intron 1 of COL4A6 at Xq22.3. The breakpoints were also identified. Possible confounding pathogenic exonic variants in genes known to be involved in other extracellular matrices disorders were also shared by the two affected individuals. Meticulous analysis of the maternal DNA revealed a case of gonosomal mosaicism.

CONCLUSIONS

This is the first report of gonadosomal mosaicism associated to DOL-AS.

Improving mutation screening in familial hematuric nephropathies through next generation sequencing

Alport syndrome is an inherited nephropathy associated with mutations in genes encoding type IV collagen chains present in the glomerular basement membrane. COL4A5 mutations are associated with the major X-linked form of the disease, and COL4A3 and COL4A4 mutations are associated with autosomal recessive and dominant forms (thought to be involved in 15% and 1%-5% of the families, respectively) and benign familial hematuria. Mutation screening of these three large genes is time-consuming and expensive. Here, we carried out a combination of multiplex PCR, amplicon quantification, and next generation sequencing (NGS) analysis of three genes in 101 unrelated patients. We identified 88 mutations and 6 variations of unknown significance on 116 alleles in 83 patients. Two additional indel mutations were found only by secondary Sanger sequencing, but they were easily identified retrospectively with the web-based sequence visualization tool Integrative Genomics Viewer. Altogether, 75 mutations were novel. Sequencing the three genes simultaneously was particularly advantageous as the mode of inheritance could not be determined with certainty in many instances. The proportion of mutations in COL4A3 and COL4A4 was notably high, and the autosomal dominant forms of Alport syndrome appear more frequently than reported previously. Finally, this approach allowed the identification of large COL4A3 and COL4A4 rearrangements not described previously. We conclude that NGS is efficient, reduces screening time and cost, and facilitates the provision of appropriate genetic counseling in Alport syndrome.

Synaptic basal lamina-associated congenital myasthenic syndromes

Proteins associated with the basal lamina (BL) participate in complex signal transduction processes that are essential for the development and maintenance of the neuromuscular junction (NMJ). Most important junctional BL proteins are collagens, such as collagen IV (α3-6), collagen XIII, and ColQ; laminins; nidogens; and heparan sulfate proteoglycans, such as perlecan and agrin. Mice lacking Colq (Colq(-/-)), laminin β2 (Lamb2(-/-)), or collagen XIII (Col13a1(-/-)) show immature nerve terminals enwrapped by Schwann cell projections that invaginate into the synaptic cleft and decrease contact surface for neurotransmission. Human mutations in COLQ, LAMB2, and AGRN cause congenital myasthenic syndromes (CMSs) owing to deficiency of ColQ, laminin-β2, and agrin, respectively. In these syndromes the NMJ ultrastructure shows striking resemblance to that of mice lacking the corresponding protein; furthermore, the extracellular localization of mutant proteins may provide favorable conditions for replacement strategies based on gene therapy and stem cells.

Alport syndrome and leiomyomatosis: the first deletion extending beyond COL4A6 intron 2

Alport syndrome (ATS) is a nephropathy characterized by the association of progressive hematuric nephritis with ultrastructural changes of the glomerular basement membrane (thinning, thickening, and splitting), sensorineural deafness, and variable ocular abnormalities (anterior lenticonus, macular flecks, and cataracts). The most common mode of transmission is X-linked inheritance, due to COL4A5 mutations. X-linked ATS is rarely associated with diffuse leiomyomatosis (DL), a benign hypertrophy of the visceral smooth muscle in gastrointestinal, respiratory, and female reproductive tracts. The ATS-DL complex is due to deletions that encompass the 5' ends of the COL4A5 and COL4A6 genes and include the bidirectional promoter. In this paper, we described 3 ATS-DL cases, 2 familial and 1 sporadic bearing a deletion encompassing the 5'-end of both the COL4A5 and COL4A6 genes, as identified by multiplex ligation-dependent probe amplification (MLPA) analysis. The array-CGH technique allowed a better definition of deletion size, confirming that the proximal breakpoint was within COL4A6 intron 2 in 2 cases. Surprisingly, 1 case had a deletion extending proximally beyond exon 3 of COL4A6, as confirmed by qPCR analysis. This is the largest deletion reported to date that has been associated with ATS-DL and this case should lead us to reconsider the mechanisms that might be involved in the development of diffuse leiomyomatosis.

Clonal overgrowth of esophageal smooth muscle cells in diffuse leiomyomatosis-Alport syndrome caused by partial deletion in COL4A5 and COL4A6 genes

This is a study of a patient who manifests all of the features of a diffuse leiomyomatosis-Alport syndrome (DL-ATS), and her two-year-old son who has already been diagnosed with Alport syndrome. Fourteen years ago, the patient underwent a partial esophageal resection followed by a replacement with jejunum. Recently, she underwent a surgical resection of the esophagus due to esophageal dysfunction. Genetic analyses of COL4A5 and COL4A6 on the X-chromosome were efficiently performed using the genomic DNA of her son. We have identified a novel deletion of 194-kb in length, encompassing COL4A5-COL4A6 promoters as well as nearly the entire large intron 1 of COL4A5 and intron 2 of COL4A6. To uncover the relationship of the esophagus-specific occurrence of the tumor and the expression of those genes, immunohistochemical analyses of type IV collagen α chains were conducted in the non-affected individuals. The esophageal smooth muscle-specific expression of α5(IV) and α6(IV) chains in the gastrointestinal tract was observed. Moreover, CAG repeat analysis of the androgen receptor gene and an immunohistochemical analysis in the leiomyoma revealed clonal overgrowth of the cells which received X-inactivation on the non-affected allele. These results may suggest that the dominant effect was caused by the partial deletion of the esophageal smooth muscle-specific genes, COL4A5 and COL4A6.

Basement membranes and human disease

In 1990, the role of basement membranes in human disease was established by the identification of COL4A5 mutations in Alport's syndrome. Since then, the number of diseases caused by mutations in basement membrane components has steadily increased as has our understanding of the roles of basement membranes in organ development and function. However, many questions remain as to the molecular and cellular consequences of these mutations and the way in which they lead to the observed disease phenotypes. Despite this, exciting progress has recently been made with potential treatment options for some of these so far incurable diseases.

Array-CGH in unclear syndromic nephropathies identifies a microdeletion in Xq22.3-q23

To investigate whether submicroscopic chromosomal deletions or duplications can be causative of unclear syndromic nephropathies, we analyzed ten patients with congenital abnormalities of the kidney and urinary tract or glomerulopathies combined with important extrarenal anomalies by whole-genome array-based comparative genomic hybridization. In a 14-year-old girl presenting with hematuria, proteinuria, mental retardation (MR), sensorineural hearing loss, dysmorphisms, and epilepsy, we detected a microdeletion in chromosome Xq22.3-q23. This deletion was verified and characterized by fluorescence in situ hybridization and multiplex ligation-dependent probe amplification analyses, found to be de novo, uniallelic and 3.3 Mb in size. Electron microscopy of a kidney biopsy showed glomerular basement membrane thinning and segmental splitting of the lamina densa compatible with Alport syndrome. Cranial magnetic resonance and diffusion tensor imaging detected a severe neuronal migration disorder with double cortex formation and pronounced reduction of the fronto-occipital tract system. Thus, in one of ten patients with unclear syndromic nephropathies we identified a previously undescribed contiguous gene syndrome at Xq22.3-q23. The microdeletion contains the X-linked Alport syndrome gene COL4A5, the MR genes FACL4 and PAK3, and parts of the X-chromosomal lissencephaly gene DCX associated with double cortex formation in girls, MR, and epilepsy. The phenotype in our patient combines features of the Alport-MR contiguous gene syndrome with lissencephaly.

The renal lesions of Alport syndrome

Alport syndrome is a hereditary, progressive, hematuric nephropathy characterized by glomerular basement membrane abnormalities with frequent hearing defects and ocular anomalies. The disease is associated with mutations in genes encoding the alpha3, alpha4, or alpha5 chains of type IV collagen, COL4A3, or COL4A4 in the autosomal forms of the disease, COL4A5 in the more frequent X-linked variety. Ultrastructural changes in the glomerular basement membrane and frequent abnormal expression of type IV collagen chains in renal and skin basement membranes are crucial elements for the diagnosis of Alport syndrome, determination of the mode of inheritance, and genetic counseling. Animal models have provided invaluable tools to study the mechanisms leading to progressive deterioration of the glomerular basement membrane and ultimately to renal failure, and to evaluate benefits of potential targeted therapies.

MLPA and cDNA analysis improves COL4A5 mutation detection in X-linked Alport syndrome

The X-linked form of Alport syndrome (AS) is caused by mutations in the COL4A5 gene encoding the alpha5 chain of type IV collagen. Most COL4A5 mutations are individual, and mutation analysis is complicated by the size of the gene and the number of exons. Larger structural rearrangements account for 10-15% of mutations. We have established a method for mutation analysis of COL4A5 based on reverse transcriptase-polymerase chain reaction analysis of mRNA from cultured skin fibroblasts and multiplex ligation-dependent probe amplification (MLPA) on genomic DNA. One advantage of using skin biopsies for the mRNA analysis is the possibility of immunohistochemical staining for the alpha5(IV) chain on skin sections to support a diagnosis of X-linked AS. A mutation was detected in all five cases included. One patient presenting with AS and diffuse leiomyomatosis was found to have a COL4A5 deletion extending into and comprising COL4A6 exons 1, 1', and 2. We have evaluated the MLPA assay on samples from 67 previously tested AS patients (45 males and 22 females) and 20 controls. We found that the combination of cDNA and MLPA analysis improves the mutation detection rate in COL4A5 and that MLPA should be the first step in genetic testing for X-linked AS.

[Alport syndrome or progressive hereditary nephritis with hearing loss]

Alport syndrome is an inherited disorder characterized by progressive hematuric nephritis with structural defects of the glomerular basement membrane, and sensorineural deafness. Ocular abnormalities are frequently associated. The incidence is approximatively 1/5000. The renal disease is severe in male patients and should be responsible for 2% of end-stage renal failure. Alport syndrome is heterogeneous at the clinical and genetic levels. It occurs as a consequence of structural abnormalities in type IV collagen, the major constituent of basement membranes. Six genetically distinct chains of type IV collagen have been identified. Mutations in the COL4A5 gene located at Xq22, and encoding the alpha 5(IV) chain are responsible for X-linked Alport syndrome whereas COL4A3 or COL4A4 located "head to head" on chromosome 2 are involved in the rarer autosomal forms of the disease.

Multiple giant leiomyomas of the esophagus and stomach

Leiomyomas are rare esophageal disorders, although among the benign esophageal neoplasms, they are the most common. Multiple leiomyomas are distinguished from esophageal leiomyomatosis, an extremely rare condition, which is associated with Alport syndrome, showing deletions and rearrangements of the COL4A5/COL4A6 gene. There are only a few reports of diffuse multilocular lesions. A 19-year-old man presented with upper gastrointestinal bleeding and diffuse abdominal pain. On endoscopy multiple nodules covered with intact mucosa were present, the largest tumor arising from the gastro-esophageal border infiltrating the cardia. Barium swallow demonstrated narrowing of the middle and lower esophagus with the upper third of the stomach filled by the tumor. Thorax and abdominal CT scans revealed infiltration of almost the total aboral esophagus by the tumor with compression of left and right bronchi. The infiltration reached the whole lesser curvature of the stomach. Endosonography showed multiple encapsulated nodules. Due to the extended tumor growth with infiltration of the upper third of the stomach, a total esophago-gastrectomy with reconstruction by colon interposition was performed. On histopathological examination multiple esophageal leiomyomas with infiltration of the proximal third of the stomach was shown. Immunohistochemically the tumor stained positive for desmin and sm-actin and negative for CD34 and c-kit. Genetic analysis ruled out a deletion of the COL4A5/COL4A6 locus on chromosome X that is linked with Alport syndrome-diffuse leiomyomatosis. Extended mutations in the COL4A5 gene, associated with Alport syndrome, to the COL4A6 gene, are required for the development of leiomyomatosis. In young patients with diffuse multinodular infiltration by encapsulated tumors, esophageal leiomyomatosis should be considered. If the proximal third of the stomach is infiltrated by the tumor an extended resection is necessary. Reconstruction procedures include colon interposition.

Cataracte congénitale

Cataract is a loss of lens transparency because of a protein alteration. Etiopathogenesis is poorly understood but new mutations of different developmental genes involved are found in 25% of cases. Frequency of onset, particularly when different ocular development anomalies occur, is related to the lens induction phenomena on the eye's anterior segment structure during embryologic development. Genetic transmission is often found on the dominant autosomal mode. Diagnosis is based on a complete and detailed examination of the eye, often with general anaesthesia. This condition predisposes children to later, sometimes serious amblyopia. Different clinical aspects can be observed: from cataract with ocular and/or systemic anomalies to polymalformative syndrome, skeletal, dermatological, neurological, metabolic, and genetic or chromosomal diseases. A general systematic pediatric examination is necessary. Congenital cataract requires first and foremost early diagnosis and a search for all etiologies. Surgical treatment is adapted case by case but it has progressed with the quality of today's intraocular lenses even if systematic implantation continues to be debated. Life-long monitoring is absolutely necessary.

Genome-wide scan for myopia in the Old Order Amish

PURPOSE

To identify myopia susceptibility genes influencing common myopia in 34 Old Order Amish families, a genetically well-defined founder population.

DESIGN

A prospective study of families with myopia consisting of a minimum of two individuals affected with myopia.

METHODS

Extended families consisting of at least two siblings affected with myopia were ascertained. A genome-wide linkage scan using 387 markers was conducted by the Center for Inherited Disease Research (CIDR). Linkage analyses were conducted with parametric (autosomal dominant, fixed penetrance model) and nonparametric methods. Model-free linkage analysis was also performed maximizing over penetrance and over dominance (that is, fitting a wide range of both dominant and recessive models).

RESULTS

Under the fixed penetrance model, the maximum two-point heterogeneity LOD score (HLOD) was 1.59 at D20S451 and the maximum multipoint HLOD was 1.92 at D6S1021. The nonparametric maximum multipoint (NPL) at D3S2427 had a P-value of .0005. Under the model-free analysis, multipoint heterogeneity LOD scores of 2.03 were observed on both chromosomes 8 (under a recessive model between D8S1130 and D8S1106) and X (under a recessive model between DXS6800 and DXS6789). Reanalyses of chromosomes 3, 6, 8, 20, and X using the best penetrance models resulted in maximum multipoint HLODs of 1.84 at D3S3053; 1.84 at D3S2427; 2.04 at D8S1130; and 2.34 at DXS6800.

CONCLUSIONS

The locus on chromosome 8p23 independently confirms a report by Hammond and associates mapping a myopia quantitative trait loci (QTL) to this region.

Familial hematurias: what we know and what we don't

Over the past 30 years we have learned a great deal about the molecular genetics and natural history of familial forms of hematuria. Our enhanced understanding of these conditions has yet to generate effective therapies for Alport syndrome, the form of familial hematuria associated with end-stage renal disease. This review briefly presents the current state of knowledge about familial hematuria and argues for the organization of clinical therapeutic trials in Alport syndrome.

A large tandem duplication within the COL4A5 gene is responsible for the high prevalence of Alport syndrome in French Polynesia

A large tandem duplication within the COL4A5 gene is responsible for the high prevalence of Alport syndrome in French Polynesia. Background. The prevalence of X-linked Alport syndrome, a progressive inherited nephropathy associated with mutations in the type IV collagen gene COL4A5, is remarkably high in French Polynesia. Methods. A vast clinical, genealogic, and molecular study was undertaken in Polynesia, based on public records, patients' interviews, linkage analysis, and mutation screening. Results and Conclusions. We show that the high frequency of Alport syndrome in this region is due to a founder mutation that occurred onto a common haplotype shared by affected and unaffected individuals, the presence of which precludes indirect molecular diagnosis. We have characterized the mutation as a tandem duplication of 35 COL4A5 exons, resulting in a approximately 65% increase in the length of the collagenous domain of the alpha 5(IV) chain, which is still able to assemble into type IV collagen network as shown by immunofluorescence analysis. That mutation is associated with severe and highly penetrant ocular symptoms and with uniformly thin glomerular basement membrane (GBM) in male adult patients. However, the rate of progression of the renal disease is very variable from one male patient to another, demonstrating the importance of strong modifier factors. Our results suggest that the 20% to 50% of "missing"COL4A5 mutations in X-linked Alport syndrome may be rearrangements similar to that reported here, which was not detectable by sequencing of either individual COL4A5 exons or overlapping cDNA fragments. Finally, we provide the basis for a polymerase chain reaction (PCR) assay that accurately identifies female carriers and allows adequate genetic counseling in this population.

Refinement of the locus for non-syndromic sensorineural deafness (DFN2)

Non-syndromic X-linked deafness is a rare form of genetic deafness in humans accounting for a small proportion of all hereditary hearing loss. Different clinical forms of non-syndromic X-linked deafness have been described, and most of these have been mapped. Here, we report a Chinese family affected by a congenital profound sensorineural hearing loss. All phenotypes of this family are clinically compatible with non-syndromic sensorineural deafness (DFN2). A maximum two-point Lod score of 2.32 was obtained at marker DXS6797 (theta = 0.00). Recombinants define a region of 4.3 cM flanked by markers DXS6799 and GATA172D05. This region overlaps the previously reported DFN2 region by 2.0 cM.

Endoscopic finding of granular cell tumour associated with leiomyomas in the oesophagus

Following a single report in the literature of granular cell tumour associated with diffuse leiomyomatosis in the oesophagus, we describe the case of a 39-year-old man in whom a granular cell tumour and two leiomyomas were endoscopically removed from this site. This previously unreported association of granular cell tumour with isolated leiomyomas suggests the need to bear in mind the possibility of other mesenchymal lesions, including leiomyomas or leiomyomatosis, when a granular cell tumour is found in the oesophagus.

Alport syndrome with diffuse leiomyomatosis

Alport syndrome (AS) is a hereditary nephropathy with hematuria progressing to end-stage renal failure (ESRF), sensorineural deafness, and specific eye signs (lenticonus, macular flecks, and congenital cataracts). Inheritance is X-linked in about 85% of the cases, caused by different mutations in the COL4A5 gene. Rarely AS is seen in combination with diffuse leiomyomatosis (DL). DL is a tumorous process involving smooth muscle cells, mostly of the esophagus, but also of the tracheobronchial tree and the female genital tract. Characteristically, the patients have deletions of the 5'-end of both the COL4A5 and the COL4A6 genes, respectively. We here present a 9-year-old boy who was admitted because of a newly diagnosed sensorineural deafness. He was born with cataracts and presented symptoms of dysphagia and bronchial irritation in the first year of life. Macroscopic hematuria was first noticed at 2 years during a febrile infection. Since early childhood the boy suffered from severe constipation. Taking together these symptoms, the diagnosis of Alport syndrome with diffuse leiomyomatosis (AS-DL) has to be considered. Genetic analysis demonstrated the predicted deletion of the COL4A5/COL4A6 genes.

The gene mutated in juvenile nephronophthisis type 4 encodes a novel protein that interacts with nephrocystin

Nephronophthisis, the most common genetic cause of chronic renal failure in children, is a progressive tubulo-interstitial kidney disorder that is inherited as an autosomal recessive trait. The disease is characterized by polyuria, growth retardation and deterioration of renal function during childhood or adolescence. The most prominent histological features are modifications of the tubules with thickening of the basement membrane, interstitial fibrosis and, in the advanced stages, medullary cysts. Nephronophthisis can also be associated with conditions affecting extrarenal organs, such as retinitis pigmentosa (Senior-Løken syndrome) and ocular motor apraxia (Cogan syndrome). Three loci are associated with the juvenile, infantile and adolescent forms, on chromosomes 2q13 (NPHP1; refs 5,6), 9q22 (NPHP2; ref. 7) and 3q21 (NPHP3; ref. 8), respectively. NPHP1, the only gene identified so far, encodes nephrocystin, which contains a Src homology 3 (SH3) domain and interacts with intracytoplasmic proteins involved in cell adhesion. Recently, a second locus associated with the juvenile form of the disease, NPHP4, was mapped to chromosome 1p36 (ref. 14). We carried out haplotype analysis of families affected with nephronophthisis that were not linked to the NPHP1, NPHP2 or NPHP3 loci, using markers covering this region. This allowed us to reduce the NPHP4 interval to a one centimorgan interval between D1S2795 and D1S2870, which contains six genes. We identified five different mutations in one of these genes, designated NPHP4, in unrelated individuals with nephronophthisis. The NPHP4 gene encodes a 1,250-amino acid protein of unknown function that we named nephrocystin-4. We demonstrated the interaction of nephrocystin-4 with nephrocystin suggesting that these two proteins participate in a common signaling pathway.

Infrequent somatic deletion of the 5' region of the COL1A2 gene in oesophageal squamous cell cancer patients

Oesophageal squamous cell cancer is the leading cause of cancer death amongst African males in South Africa. DNA was isolated from normal and tumour biopsies of the oesophagi of 33 African patients with squamous cell carcinoma of the oesophagus and was analysed with two dinucleotide repeat polymorphisms, a GT repeat sequence in the first intron, and a CA repeat in the promoter of the human alpha2(I) procollagen gene (COL1A2), using the polymerase chain reaction (PCR). Normal and tumour DNAs from each individual were compared to identify changes present in the tumour DNA, but absent in normal DNA. Twenty two cases were informative (heterozygous) for the promoter polymorphism and 24 cases were informative for the intronic polymorphism. Loss of heterozygosity (LOH) was seen in 2/22 (9.1%) for the promoter and 3/24 (12.5%) for the intronic polymorphism. These changes involved a total of three patients: two patients displayed the lost allele incorporating both the CA repeat and GT repeat loci; the third patient revealed LOH at the intronic polymorphism, but was non-informative (homozygous) for the promoter polymorphism. Deletions within the procollagen genes may represent an as yet unrecognised but rare event in the multistep process of carcinogenesis.

Multiple cutaneous and uterine leiomyomas: refinement of the genetic locus for multiple cutaneous and uterine leiomyomas on chromosome 1q42.3-43

Cutaneous leiomyomas, rare benign tumors originating from the arrector pili muscle of the hair follicle, can be associated with the common uterine fibroids in a syndrome called multiple cutaneous and uterine leiomyomas. Multiple cutaneous and uterine leiomyomas are inherited as an autosomal dominant trait, providing an excellent opportunity for the study of the common non-Mendelian manifestation of isolated uterine fibroids. This study reports the clinical and molecular characterization of an extended family with multiple cutaneous and uterine leiomyomas. Linkage analysis has shown that the disease in this family is linked to the recently reported genetic locus for multiple cutaneous and uterine leiomyomas, with a maximum two-point LOD score of 4.453 for markers D1S2670, D1S2785, D1S547, and D1S1609. The identification of key recombination events has allowed us to refine substantially the location of the genetic locus for multiple cutaneous and uterine leiomyomas, from 14 cM to an interval of 4.55 or 7.19 cM, depending on the final phenotype of a young family member in which one of the key recombination events has occurred. In addition, we provide a description of the interesting pattern and progression of the skin phenotype in this four-generation kindred. The refinement of the genetic locus for multiple cutaneous and uterine leiomyomas and the availability of an extended multigeneration pedigree will facilitate the identification of the mutated gene responsible for multiple cutaneous and uterine leiomyomas, which, in turn, may provide key information for the understanding of the molecular basis of the common uterine fibroids.

Alport syndrome associated with diffuse leiomyomatosis: COL4A5-COL4A6 deletion associated with a mild form of Alport nephropathy

BACKGROUND

The X-linked Alport syndrome (AS) is an inherited nephropathy due to mutations in the COL4A5 gene, encoding the alpha5 chain of type IV collagen, a major component of the glomerular basement membrane (GBM). Here, we report a new kindred with the rare association of X-linked AS and diffuse leiomyomatosis (DL), which is a tumourous process involving smooth muscle cells of the oesophagus, the tracheobronchial tree and, in females, the genital tract. For this syndrome, an almost constant association of large COL4A5 rearrangements with a severe juvenile form of nephropathy has been described for male patients.

METHODS

DNA rearrangement at the COL4A5-COL4A6 locus was studied in several members of this family using polymerase chain reaction and pulsed field gel electrophoresis. Furthermore, immunohistochemical staining of tumour and skin samples was performed.

RESULTS

The affected patients in this family carry a 120 kb deletion by which the COL4A5 exon 1 and COL4A6 exons 1, 1', and 2 are removed. Immunohistochemical investigation of a skin biopsy of an affected male patient confirmed the absence of both the alpha5 and the alpha6 chains of type IV collagen in the basement membrane of the skin. Surprisingly, both affected male patients had a rather mild renal phenotype.

CONCLUSIONS

This report shows that, contrary to what has been reported to date, patients suffering from AS associated with DL can be associated with a late onset renal failure (adult) form of nephropathy.

The NC1 domain of collagen IV encodes a novel network composed of the alpha 1, alpha 2, alpha 5, and alpha 6 chains in smooth muscle basement membranes

Type IV collagen, the major component of basement membranes (BMs), is a family of six homologous chains (alpha1-alpha6) that have a tissue-specific distribution. The chains assemble into supramolecular networks that differ in the chain composition. In this study, a novel network was identified and characterized in the smooth muscle BMs of aorta and bladder. The noncollagenous (NC1) hexamers solubilized by collagenase digestion were fractionated by affinity chromatography using monoclonal antibodies against the alpha5 and alpha6 NC1 domains and then characterized by two-dimensional gel electrophoresis and Western blotting. Both BMs were found to contain a novel alpha1.alpha2.alpha5.alpha6 network besides the classical alpha1.alpha2 network. The alpha1.alpha2.alpha5.alpha6 network represents a new arrangement in which a protomer (triple-helical isoform) containing the alpha5 and alpha6 chains is linked through NC1-NC1 interactions to an adjoining protomer composed of the alpha1 and alpha2 chains. Re-association studies revealed that the NC1 domains contain recognition sequences sufficient to encode the assembly of both networks. These findings, together with previous ones, indicate that the six chains of type IV collagen are distributed in three major networks (alpha1.alpha2, alpha3.alpha4.alpha5, and alpha1.alpha2.alpha5.alpha6) whose chain composition is encoded by the NC1 domains. The existence of the alpha1.alpha2.alpha5.alpha6 network provides a molecular explanation for the concomitant loss of alpha5 and alpha6 chains from the BMs of patients with X-linked Alport's syndrome.

Diffuse esophageal leiomyomatosis with perirectal involvement mimicking Hirschsprung disease

We describe a 25-year-old woman with diffuse esophageal leiomyomatosis. During childhood, achalasia was mistakenly diagnosed in this patient. Subsequently, she underwent cardiomyotomy and developed symptoms of Hirschsprung disease. These symptoms were caused by infiltration of the esophageal and rectal walls by benign muscular hypertrophy. The pseudo-Hirschsprung disorder was manifested by chronic severe constipation, with consistent manometric findings. Clitoral hypertrophy and vulvar and periurethral leiomyoma were also present. Genetic analysis demonstrating deletion of the COL4A5/COL4A6 locus and the discovery of microscopic hematuria implied that the patient could transmit both diffuse leiomyomatosis and the Alport syndrome.

The clinical spectrum of type IV collagen mutations

Clinical manifestations of type IV collagen mutations can vary from the severe, clinically and genetically heterogeneous renal disorder, Alport syndrome, to autosomal dominant familial benign hematuria. The predominant form of Alport syndrome is X-linked; more than 160 different mutations have yet been identified in the type IV collagen alpha 5 chain (COL4A5) gene, located at Xq22-24 head to head to the COL4A6 gene. The autosomal recessive form of Alport syndrome is caused by mutations in the COL4A3 and COL4A4 genes, located at 2q35-37. Recently, the first mutation in the COL4A4 gene was identified in familial benign hematuria. This paper presents an overview of type IV collagen mutations, including eight novel COL4A5 mutations from our own group in patients with Alport syndrome. The spectrum of mutations is broad and provides insight into the clinical heterogeneity of Alport syndrome with respect to age at renal failure and accompanying features such as deafness, leiomyomatosis, and anti-GBM nephritis.

X-linked Alport syndrome: natural history in 195 families and genotype- phenotype correlations in males

Alport syndrome (AS) is a type IV collagen hereditary disease characterized by the association of progressive hematuric nephritis, hearing loss, and, frequently, ocular changes. Mutations in the COL4A5 collagen gene are responsible for the more common X-linked dominant form of the disease. Considerable allelic heterogeneity has been observed. A "European Community Alport Syndrome Concerted Action" has been established to delineate accurately the AS phenotype and to determine genotype-phenotype correlations in a large number of families. Data concerning 329 families, 250 of them with an X-linked transmission, were collected. Characteristics of the 401 male patients belonging to the 195 families with COL4A5 mutation are presented. All male patients were hematuric, and the rate of progression to end-stage renal failure and deafness was mutation-dependent. Large deletions, non-sense mutations, or small mutations changing the reading frame conferred to affected male patients a 90% probability of developing end-stage renal failure before 30 yr of age, whereas the same risk was of 50 and 70%, respectively, in patients with missense or splice site mutation. The risk of developing hearing loss before 30 yr of age was approximately 60% in patients with missense mutations, contrary to 90% for the other types of mutations. The natural history of X-linked AS and correlations with COL4A5 mutations have been established in a large cohort of male patients. These data could be used for further evaluation of therapeutic approaches.

Characterization of the NPHP1 locus: mutational mechanism involved in deletions in familial juvenile nephronophthisis

Familial juvenile nephronophthisis is an autosomal recessive, genetically heterogeneous kidney disorder representing the most frequent inherited cause of chronic renal failure in children. A gene, NPHP1, responsible for approximately 85% of the purely renal form of nephronophthisis, has been mapped to 2q13 and characterized. The major NPHP1 gene defect is a large homozygous deletion found in approximately 80% of the patients. In this study, by large-scale genomic sequencing and pulsed-field gel electrophoresis analysis, we characterized the complex organization of the NPHP1 locus and determined the mutational mechanism that results in the large deletion observed in most patients. We showed that the deletion is 290 kb in size and that NPHP1 is flanked by two large inverted repeats of approximately 330 kb. In addition, a second sequence of 45 kb located adjacent to the proximal 330-kb repeat was shown to be directly repeated 250 kb away within the distal 330-kb repeat deleting the sequence tag site (STS) 804H10R present in the proximal copy. The patients' deletion breakpoints appear to be located within the 45-kb repeat, suggesting an unequal recombination between the two homologous copies of this smaller repeat. Moreover, we demonstrated a nonpathologic rearrangement involving the two 330-kb inverted repeats found in 11 patients and, in the homozygous state, in 2 (1.3%) control individuals. This could be explained by interchromosomal mispairing of the 330-kb inverted repeat, followed by double recombination or by a prior intrachromosomal mispairing of these repeats, leading to an inversion of the NPHP1 region, followed by an interchromosomal unequal crossover event. This complex rearrangement, as well as the common deletion found in most patients, illustrates the high level of rearrangements occurring in the centromeric region of chromosome 2.

Genetic linkage of autosomal-dominant Alport syndrome with leukocyte inclusions and macrothrombocytopenia (Fechtner syndrome) to chromosome 22q11-13

Fechtner syndrome is an autosomal-dominant variant of Alport syndrome, manifested by nephritis, sensorineural hearing loss, cataract formation, macrothrombocytopenia, and polymorphonuclear inclusion bodies. As opposed to autosomal-recessive and X-linked Alport syndromes, which have been genetically well studied, the genetic basis of Fechtner syndrome remains elusive. We have mapped the disease-causing gene to the long arm of chromosome 22 in an extended Israeli family with Fechtner syndrome plus impaired liver functions and hypercholesterolemia in some individuals. Six markers from chromosome 22q yielded a LOD score >3.00. A maximum two-point LOD score of 7.02 was obtained with the marker D22S283 at a recombination fraction of 0. Recombination analysis placed the disease-causing gene in a 5.5-Mb interval between the markers D22S284 and D22S1167. No collagen genes or genes comprising the basement membrane have been mapped to this region.

Alport syndrome. An inherited disorder of renal, ocular, and cochlear basement membranes

Alport syndrome (AS) is a genetically heterogeneous disease arising from mutations in genes coding for basement membrane type IV collagen. About 80% of AS is X-linked, due to mutations in COL4A5, the gene encoding the alpha 5 chain of type IV collagen (alpha 5[IV]). A subtype of X-linked Alport syndrome (XLAS) in which diffuse leiomyomatosis is an associated feature reflects deletion mutations involving the adjacent COL4A5 and COL4A6 genes. Most other patients have autosomal recessive Alport syndrome (ARAS) due to mutations in COL4A3 or COL4A4, which encode the alpha 3(IV) and alpha 4(IV) chains, respectively. Autosomal dominant AS has been mapped to chromosome 2 in the region of COL4A3 and COL4A4. The features of AS reflect derangements of basement membrane structure and function resulting from changes in type IV collagen expression. The primary pathologic event appears to be the loss from basement membranes of a type IV collagen network composed of alpha 3, alpha 4, and alpha 5(IV) chains. While this network is not critical for normal glomerulogenesis, its absence appears to provoke the overexpression of other extracellular matrix proteins, such as the alpha 1 and alpha 2(IV) chains, in glomerular basement membranes, leading to glomerulosclerosis. The diagnosis of AS still relies heavily on histologic studies, although routine application of molecular genetic diagnosis will probably be available in the future. Absence of epidermal basement membrane expression of alpha 5(IV) is diagnostic of XLAS, so in some cases kidney biopsy may not be necessary for diagnosis. Analysis of renal expression of alpha 3(IV)-alpha 5(IV) chains may be a useful adjunct to routine renal biopsy studies, especially when ultrastructural changes in the GBM are ambiguous. There are no specific therapies for AS. Spontaneous and engineered animal models are being used to study genetic and pharmacologic therapies. Renal transplantation for AS is usually very successful. Occasional patients develop anti-GBM nephritis of the allograft, almost always resulting in graft loss.

Absence of the alpha6(IV) chain of collagen type IV in Alport syndrome is related to a failure at the protein assembly level and does not result in diffuse leiomyomatosis

X-linked Alport syndrome is a progressive nephropathy associated with mutations in the COL4A5 gene. The kidney usually lacks the alpha3-alpha6 chains of collagen type IV, although each is coded by a separate gene. The molecular basis for this loss remains unclear. In canine X-linked hereditary nephritis, a model for X-linked Alport syndrome, a COL4A5 mutation results in reduced mRNA levels for the alpha3, alpha4, and alpha5 chains in the kidney, implying a mechanism coordinating the production of these 3 chains. To examine whether production of alpha6 chain is under the same control, we studied smooth muscle cells from this animal model. We determined the canine COL4A5 and COL4A6 genes are separated by 435 bp, with two first exons for COL4A6 separated by 978 bp. These two regions are >/= 78% identical to the human sequences that have promoter activity. Despite this potential basis for coordinated transcription of the COL4A5 and COL4A6 genes, the alpha6 mRNA level remained normal in affected male dog smooth muscle while the alpha5 mRNA level was markedly reduced. However, both alpha5 and alpha6 chains were absent at the protein level. Our results suggest that production of the alpha6 chain is under a control mechanism separate from that coordinating the alpha3-alpha5 chains and that the lack of the alpha6 chain in Alport syndrome is related to a failure at the protein assembly level, raising the possibility that the alpha5 and alpha6 chains are present in the same network. The lack of the alpha6 chain does not obviously result in disease, in particular leiomyomatosis, as is seen in Alport patients with deletions involving the COL4A5 and COL4A6 genes.

LINE-1 elements at the sites of molecular rearrangements in Alport syndrome-diffuse leiomyomatosis

Deletions encompassing the 5' termini of the paired type IV collagen genes COL4A5 and COL4A6 on chromosome Xq22 give rise to Alport syndrome (AS) and associated diffuse leiomyomatosis (DL), a syndrome of disseminated smooth-muscle tumors involving the esophagus, large airways, and female reproductive tract. In this study, we report isolation and characterization of two deletion junctions. The first, in a patient described elsewhere, arose by a nonhomologous recombination event fusing a LINE-1 (L1) repetitive element in intron 1 of COL4A5 to intron 2 of COL4A6, resulting in a 13.4-kb deletion. The second, in a previously undescribed family, arose by unequal homologous recombination between the same L1 and a colinear L1 element in intron 2 of COL4A6, resulting in a>40-kb deletion. L1 elements have contributed to the emergence of this locus as a site of frequent recombinations by diverse mechanisms. These give rise to AS-DL by disruption of type IV collagen and perhaps other as yet unidentified genes, evidenced by deletions as small as 13.4 kb.

Diffuse leiomyomatosis of the esophagus: disorder of cell-matrix interaction?

Diffuse leiomyomatosis (DL) is rare condition characterized by proliferation of smooth muscle in the upper gastrointestinal tract. Most cases are associated with X-linked Alport syndrome and have partial deletions in the genes encoding both the alpha5 and alpha6 chains of collagen type IV. We studied aspects of cell-matrix interaction of myocytes in an esophagogastrectomy specimen from a 12-year-old patient with DL. Myocytes had central areas of cytoplasmic rarefaction, which were actin positive and desmin poor, with the reverse pattern of staining at the cell periphery. Electron microscopy (EM) showed that the areas of rarefaction consisted of disorganized aggregates of filaments. The basement membranes ranged from thickened to thinned or absent. Immunohistochemical staining for the alpha1-alpha4 chains of collagen type IV, the alpha1, alpha2, beta2, and gamma1 chains of laminin, nidogen, type VI collagen, and fibronectin was normal. There was loss of the alpha5 and alpha6 chains of collagen type IV and the beta1 chain of laminin. Normal staining for alpha1, alpha2, alpha3, alpha4, alpha6, alpha8, and beta1 integrins was noted. Staining for alpha5 integrin varied from normal to reduced or negative in different cells. In DL, a primary abnormality of basement membrane may be associated with disorganization of the contractile apparatus and alterations of certain integrins. This may reflect a disturbance of cell-matrix interactions that play a role in cell differentiation and internal organization.

[What's new in pediatric nephrology?]

Advances in pediatric nephrology has been mainly characterized during the last years by a burst of knowledge in the area of genetic renal diseases: 1/almost complete understanding of Alport syndrome related to mutations of COL4A5 or COL4A3/A4 genes of collagene; 2/the mapping and cloning of the nephronophthisis gene which is deleted in 75% of cases; 3/the mapping and cloning of the cystinosis gene coding for a protein of the lysosomal membrane; 4/the mapping and cloning of the Finnish-type congenital nephrotic syndrome gene; 5/the linkage to the SNR 1 gene on chromosome 1 of a large number of familial corticoresistant nephrotic syndromes, and the disclosure of mutations of the WT1 gene in diffuse mesangial sclerosis and in Frazier syndrome. The understanding of Bartter syndrome has been also enlightened by the discovery of mutations in several ionic channels located in the distal tubule. It has been also shown that a corticoresistant nephrotic syndrome or a chronic tubular interstitial nephropathy are possible phenotypes for mitochondrial cytopathies. In the area of therapeutics, recombinant growth hormone was shown to improve statural growth of children with chronic renal failure; in addition, renal transplantation benefits from new immunosuppressants as tacrolimus and mycophenolate mofetil.

X-linked Alport syndrome in females

Alport syndrome (AS) is in the differential diagnosis of hematuria. Variability in clinical presentation and in the ultrastructural changes of the glomerulus can make the diagnosis of AS a challenge in female patients. The purpose of this report is to present immunostaining for glomerular basement membrane (GBM) expression of alpha5(IV) as an adjunctive diagnostic method. Renal biopsy specimens from eight female patients with clinical presentation suggestive of AS were studied. The patients were between 7 and 36 years of age; six were between 12 and 15 years. Light microscopy and immunohistochemistry using a monoclonal antibody to alpha5(IV) were performed. Controls showed a continuous linear pattern along the GBM in normal kidneys and absence in renal biopsy specimens from male X-linked AS patients. To express the variability of the ultrastructural GBM changes among the patients in the series, we developed a semi-quantitative Alport Index, obtained by quantification of severity and extent of ultrastructural GBM changes. With immunohistochemistry, we showed an interrupted, discontinuous linear pattern for alpha5(IV) in glomeruli from the eight patients in the series, confirming the diagnosis of X-linked AS. The ultrastructural Alport Index varied between 6 and 47, showing the heterogeneity in the severity of the GBM changes, even among the six patients aged between 12 and 15 years. In three of the eight biopsy specimens, the predominant change was thin GBM, and the Alport Index was below 20. Immunohistochemistry for alpha5(IV) in renal biopsy specimens can identify female patients heterozygous for X-linked AS. In this series, the method led to the diagnosis of AS in female patients in whom the predominant ultrastructural change was thin basement membrane.

Alport syndrome, mental retardation, midface hypoplasia, and elliptocytosis: a new X linked contiguous gene deletion syndrome?

We describe a family with four members, a mother, two sons, and a daughter, who show clinical features consistent with X linked Alport syndrome. The two males presented with additional features including mental retardation, dysmorphic facies with marked midface hypoplasia, and elliptocytosis. The elliptocytosis was not associated with any detectable abnormalities in red cell membrane proteins; red cell membrane stability and rigidity was normal on ektacytometry. Molecular characterisation suggests a submicroscopic X chromosome deletion encompassing the entire COL4A5 gene. We propose that the additional abnormalities found in the affected males of this family are attributable to deletion or disruption of X linked recessive genes adjacent to the COL4A5 gene and that this constellation of findings may represent a new X linked contiguous gene deletion syndrome.

Topoisomerase I and II consensus sequences in a 17-kb deletion junction of the COL4A5 and COL4A6 genes and immunohistochemical analysis of esophageal leiomyomatosis associated with Alport syndrome

Diffuse esophageal leiomyomatosis (DL), a benign smooth-muscle-cell tumor, is characterized by abnormal cell proliferation. DL is sometimes associated with X-linked Alport syndrome (AS), an inherited nephropathy caused by COL4A5 gene mutations. COL4A5 is tightly linked, in a head-to-head fashion, to the functionally related and coordinately regulated COL4A6 gene. No X-linked AS cases are due to COL4A6 mutations, but all DL/AS cases are always associated with deletions spanning the 5' regions of the COL4A5/COL4A6 cluster. Unlike the COL4A5 breakpoints, those of COL4A6 are clustered within intron 2 of the gene. We identified a DL/AS deletion and the first characterization of the breakpoint sequences. We show that a deletion eliminates the first coding exon of COL4A5 and the first two coding exons of COL4A6. The breakpoints share the same sequence, which, in turn, is closely homologous to the consensus sequences of topoisomerases I and II. Additional DNA evidence suggested that the male patient is a somatic mosaic for the mutation. Immunohistochemical analysis using alpha-chain-specific monoclonal antibodies supported this conclusion, since it revealed the absence of the alpha5(IV) and alpha6(IV) collagen chains in most but not all of the basement membranes of the smooth-muscle-cell tumor. We also documented a similar segmental staining pattern in the glomerular basement membranes of the patient's kidney. This study is particularly relevant to the understanding of DL pathogenesis and its etiology.

FACL4, a new gene encoding long-chain acyl-CoA synthetase 4, is deleted in a family with Alport syndrome, elliptocytosis, and mental retardation

We observed a family in which two boys were diagnosed with Alport syndrome, elliptocytosis, and mental retardation and carried a large deletion of the Xq22.3-q23 region, encompassing the COL4A5 gene. This suggests the possibility of a new contiguous gene syndrome. In an attempt to characterize the genes contributing to this complex phenotype, we have isolated a gene encoding a new long-chain acyl-CoA synthetase (FACL4 or LACS4) from the region deleted in these patients. Among several ESTs identified by searching the human gene map database maintained at the National Center for Biotechnology Information, using the map position as a query, only one was deleted in the patients. RACE products containing the entire ORF were subsequently generated. Northern blot analysis showed a 5-kb mRNA expressed in several tissues except for liver and lung. Brain shows a longer transcript, possibly reflecting the use of a brain-specific upstream ATG start codon. FACL4 encodes a predicted protein product of 670 amino acids (711 in brain), with a remarkable level of conservation compared to the rat acyl-CoA synthetases ACS4 and brain-specific ACS3 protein sequences. We are investigating the possibility that the absence of this enzyme may play a role in the development of mental retardation or other signs associated with Alport syndrome in the family.